In the use of conventional acid catalysts exemplified by Brønsted acid such as a fuming sulfuric acid and the like or Lewis acid such as aluminium chloride, titanium tetrachloride and the like, there have been some disadvantages, for example, where a reaction is stoichiometric and a reaction solvent is limited. Hence a process for synthesis has been desired to be modified to be harmonized with the environment. The Beckmann rearrangement using a fuming sulfuric acid and the Friedel-Crafts acylation using aluminium chloride are a reaction in which a product and a catalyst form a stable additive and therefore not catalytic, so that the acid must be neutralized or decomposed to extract the product and consumed in a stoichiometric amount or more. Moreover, in the synthesis of acetophenone using benzene and acetyl chloride, a waste caused by neutralization of a waste aluminium chloride reaches 7.3 times the product.
Accordingly, the development of solid acid catalysts has become made in view of green chemistry. The solid acid catalysts are becoming used also for alkylation of aromatic compounds, though aluminium chloride has conventionally mainly been used therefor, so that most of the catalysts are replaced with zeolite catalysts (MCM-22 (MWW)) or the like in the process for synthesizing ethylbenzene or cumene. With this, a waste such as a waste catalyst, a waste salt and the like is largely reduced to solve a problem of corrosion of apparatuses and a problem of toxicity, and additionally, the continuous productivity is confirmed improved in environmental harmony and stability. Thus, advantages of solid catalysts are fully taken on a synthesis reaction of an organic compound having a commercial high temperature process-applicable and relatively simple structure. These solid acid catalysts are referred to as heterogeneous catalysts and particularly useful for synthesis of products in basic chemical industry, exhaust gas purification and the like, and therefore heavily used.
On the other hand, organic metal complexes and organic acids have been used as a catalyst in organic synthesis reactions of various conditions. These compounds having catalytic action are soluble in various organic solvents so as to be extremely useful for an organic synthesis or polymer synthesis in a liquid phase, and therefore molecules having a sulfonic acid group, such as conventionally known sulfuric acid, methanesulfonic acid and the like, have been developed as catalyst.
Of these compounds, an organic acid substituted with a trifluoromethanesulfonyl (triflyl, CF3SO2) group that exhibits a greatly strong electron-withdrawing property is known as a super strong acid of which acidity is equal to or higher than the acidity of sulfuric acid. Bis(trifluoromethanesulfonyl)methane where two triflyl groups are bonded to the same carbon and tris(trifluoromethanesulfonyl)methide where three triflyl groups are bonded to the same carbon can be cited also as an example of a compound exhibiting a strong acidity.
Attempts to produce strongly acidic compounds and attempts to apply these compounds as a catalyst to synthesis reactions of pharmaceuticals, agrochemicals, polymers or an intermediate of these (e.g., Friedel-Crafts alkylation reaction, Diels-Alder reaction and the like) have hitherto been made. For example, in Patent Publication 1, there are disclosed arylbis(perfluoroalkylsulfonyl)methane, a metal salt of the same, and processes for producing these.
Moreover, in Patent Publication 2, a compound represented by the general formula M[RfSO2—N—SO2Rf′]n or M[RfSO2—N—SO2Rf′]n-mH2O [where each of Rf and Rf′ is a C1-C8 perfluoroalkyl group, M is an element selected from alkali metals, alkaline earth metals, transition metals, Pb, As, Sb, Bi, Se and Te, (n) is an integer equal to the valence of a corresponding metal, and (m) is a natural number of 0.5-20.] is disclosed as a Lewis acid catalyst of which catalytic activity in an organic synthesis reaction caused by electron withdrawing reaction is increased. There are also disclosed in Patent Publication 3 organic synthesis reactions using complexes of various perfluoroalkanesulfonylimide groups and organic synthesis reactions caused by various electrophilic reactions using such complexes as catalysts.
Furthermore, in Patent Publication 4, a high activity Lewis acid catalyst usable even under coexistence of water is disclosed, the catalyst consisting of; a particular metallic halide represented by general formula M+(X1−)q (in the formula, M is at least one kind of metal selected from the group consisting of groups IIIA to VB elements of the periodic Table, X1 is a halogen atom and (q) is an integer equal to the valence of M.); and a quaternary salt type anion exchange resin.
Additionally, in Patent Publication 5, there is disclosed an acid catalyst formed including a tris(perfluoroalkylsulfonyl)methide metal salt represented by the following formula [(RfSO2)3C]nM2  [where Rf is a perfluoroalkyl group having a carbon number of 1 or more, M2 is an element selected from alkali metals, alkaline-earth metals, transition metals including rare earth elements, zinc, cadmium, aluminium, gallium, indium, thallium, silicon, germanium, tin, lead, arsenic, antimony, bismuth, selenium, and tellurium, and (n) is the same integer as the valence of M2].
Moreover, a technique relating to the invention of the present application is disclosed in Patent Publication 6, and more specifically, 1,1,3,3-tetrakis(trifluoromethanesulfonyl)propane ((CF3SO2)2CHCH2CH(SO2CF3)2; Tf2CHCH2CHTf2) is disclosed as an acid catalyst useful for a carbon-carbon bond forming reaction. Additionally, Patent Publication 7 discloses a method for producing 1,1-bis(trifluoromethanesulfonyl)ethene ((CF3SO2)2C═CH2) which is able to behave as the raw material of the propane. Furthermore, in Non-Patent Publication 1, a method for producing 1,1-bis((trifluoromethyl)sulfonyl)ethane and 1,1-bis((trifluoromethyl)sulfonyl)phenylethane is disclosed.
Incidentally, Non-Patent Publication 2 discloses various reactions for forming a carbon-carbon skeleton, in which the above-mentioned 1,1,3,3-tetrakis(trifluoromethanesulfonyl)propane is used as an acid catalyst.